The invention relates to a method of operating a sewing installation comprising a work piece holder of a geometry that corresponds to the outer contour of the work piece to be fixed thereon, the work piece holder being displaceable relative to a sewing needle via a control unit by the aid of x-y-drive motors, and a storage medium being disposed on the work piece holder; and to a corresponding sewing installation.
A sewing installation of the generic type is known for instance from DE 34 31 061 A1 (corresponding to U.S. Pat. No. 4,548,142). A work piece holder is described to be identified by the aid of a code which is formed by two surface areas which are optically reflecting or non-reflecting, the combination thereof correspondingly offering six possibilities of encoding.
EP 0 269 287 B1 specifies the optical scanning of the configuration of work pieces for the possibility of detection of how the work pieces are oriented, based on a comparison with stored work piece patterns relative to a tool.
DE 32 46 027 T1 (corresponding to U.S. Pat. No. 4,479,446) discloses a sewing machine which allows stitch patterns to be allocated to the work pieces to be sewn. The work pieces are disposed on pallets which have a binary code. Allocation of the stitch patterns takes place by detection of this binary code.
The known work piece encoding systems have in common that tables must be prepared in the control unit on the side of the sewing machine for the generation of sewing patterns, these tables, after identification of the work piece holder based on type, size and configuration, then allowing the preparation of a corresponding sewing program.
It is an object of the invention to embody a method and a sewing installation of the type mentioned at the outset such that the program for processing a certain sewing pattern will be even simpler and can be put into practice independently of data stored on the side of the sewing installation.
According to the invention, this object is attained by a method wherein provision is made for any information necessary for the control of the sewing installation to be stored in a storage medium that is disposed on the work piece holder so that, after this information has been read out, the course of the seam is computed and sewn in the sewing installation, corresponding to the contour of the work piece holder, with a given stitch length being fed into the control unit, and with the computing device of the control unit modifying the given stitch length in dependence on the computed outer contour of the work piece holder for an integral number of stitches to result.
In a sewing installation for putting this method into practice, it is provided that a storage medium is disposed on the work piece holder, comprising the entire information necessary for the control of the sewing installation, in order for the course of the seam to be computed and sewn, corresponding to the contour of the work piece holder, the sewing installation having a sensor unit designed for reading the information out of the storage medium and feeding the information to an input of the sewing-machine control unit, it being possible to input a stitch length in the control unit, with the computing device of the control unit modifying the given stitch length in dependence on the computed outer contour of the work piece holder for an integral number of stitches to result.
In keeping with a further development of the invention, it is provided that the storage medium is a chip. In as much as a chip is mentioned in this context, this refers very generally to an arrangement which enables information to be fed in, stored and read out at least once.
When the size of the work piece holder is modifiable, this is also taken into account in the modification of the stitch length.
By advantage, provision can be made for an input equipment for the manual input of a stitch length. As a rule, the stitch length is also stored on the storage medium and read out automatically. However, situations are conceivable, in which it is desirable, for purposes of modification or correction, to change the stitch length stored on the storage medium. To this end provision is made for the manual input equipment.
By advantage, the sensor unit is disposed underneath the table board, preferably in a recess thereof, in the form of a wire coil as an antenna. This helps contacting the storage medium to be read out in a close, non-contact way, simultaneously ensuring protected accommodation that does not interfere with the sewing job.
The invention differs from the prior art sewing installations and modes of operation in that the encoding applied to the work piece holder allows not only identification thereof and correspondingly the preparation of a seam program in combination with tables stored on the side of the sewing machine, but it ensures that solely the set of data stored on the work piece holder, in particular in a chip, is sufficient, and contains any information necessary, for the desired seam to be sewn regardless of the sewing machine on which the work piece holder is employed. This helps achieve a high degree of simplification of the procedure between the manufacturer of the work piece holder and the operator of the sewing installation, because the chip of the work piece holder is programmable entirely independently of the storage contents of the sewing installation.